Shenfun -- automating the spectral Galerkin method

With the shenfun Python module (github.com/spectralDNS/shenfun) an effort is made towards automating the implementation of the spectral Galerkin method for simple tensor product domains, consisting of (currently) one non-periodic and any number of periodic directions. The user interface to shenfun is intentionally made very similar to FEniCS (fenicsproject.org). Partial Differential Equations are represented through weak variational forms and solved using efficient direct solvers where available. MPI decomposition is achieved through the {mpi4py-fft} module (bitbucket.org/mpi4py/mpi4py-fft), and all developed solver may, with no additional effort, be run on supercomputers using thousands of processors. Complete solvers are shown for the linear Poisson and biharmonic problems, as well as the nonlinear and time-dependent Ginzburg-Landau equation.Comment: Presented at MekIT'17, the 9th National Conference on Computational Mechanic

Slaving in Australian courts: blackbirding cases, 1869-1871

This article examines major prosecutions in New South Wales and Queensland for blackbirding practices in Melanesian waters, and early regulation under the Imperial Kidnapping Act that was meant to correct problems those prosecutions raised. It considers how legal argument and adjudication appropriated the political debate on the question whether the trade in Melanesian labour to Queensland and Fiji amounted to slaving, and whether references to slaving in Australian courts only compounded the difficulties of deterring recruiting abuses in Melanesia. It is suggested that, even though the Imperial Government conceived of the Kidnapping Act as a measure to deal with slaving, its success in Australian courts depended on its avoiding any reference to the idea of slavery in the legislation itself. This is developed in three parts. Part 1 provides the social context, introducing the trade in Melanesian labour for work in Queensland. Part 2 explores the prosecutions brought under the slave trade legislation and at common law against labour recruiters, especially those arising from incidents involving the Daphne and the Jason. It attempts to uncover the way that lawyers in these cases used arguments from the broader political debate as to whether the trade amounted to slaving. Part 3 concludes with an account of the relatively more effective regulation brought by the Kidnapping Act, with tentative suggestions as to how the arguments about slaving in Australian courts influenced the form that regulation under the Act had to take

Comment on "Pinched Flow Fractionation: Continuous Size Separation of Particles Utilizing a Laminar Flow Profile in a Pinched Microchannel"

[First paragraph] In a recent paper Yamada et al. propose the novel concept of "pinched flow fractionation" (PFF) for the continuous size separation and analysis of particles in microfabricated lab-on-a-chip devices. In their description of the basic principle they claim that especially the width of the pinched and broadened segments will affect theseparation performance. In the following we comment on the physics behind this statement.Comment: Comment on paper by Yamada et al. [Anal. Chem. 76(18), 5465 - 5471 (2004)]. Accepted for Anal. Che

Effective area of photonic crystal fibers

We consider the effective area A_eff of photonic crystal fibers (PCFs) with a triangular air-hole lattice in the cladding. It is first of all an important quantity in the context of non-linearities, but it also has connections to leakage loss, macro-bending loss, and numerical aperture. Single-mode versus multi-mode operation in PCFs can also be studied by comparing effective areas of the different modes. We report extensive numerical studies of PCFs with varying air hole size. Our results can be scaled to a given pitch and thus provide a general map of the effective area. We also use the concept of effective area to calculate the "phase" boundary between the regimes with single-mode and multi-mode operation.Comment: 8 pages including 5 figures. Webpage at http://www.crystal-fibre.co